
@article{lindsay_moltres_2018,
	title = {Moltres: finite element based simulation of molten salt reactors},
	volume = {3},
	shorttitle = {Moltres},
	doi = {10.21105/joss.00298},
	abstract = {Moltres is a physics application for multiphysics modeling of fluid-fueled molten salt reactors
(MSRs) (Lindsay et al. 2018). It couples equations for neutron diffusion, thermal
hydraulics, and delayed neutron precursor transport. Neutron diffusion and precursor
transport equations are set-up using an action system that allows the user to use an arbitrary
number of neutron energy and precursor groups respectively with minimal input
changes. Moltres sits on top of the Multi-physics Object-Oriented Simulation Environment
(Gaston et al. 2015) and hence uses the finite element method to discretize the
governing partial differential equations. In general the resulting system of non-linear algebraic
equations is linearized using the Newton-Raphson method and then solved using
the Portable, Extensible Toolkit for Scientific Computation (Balay et al. 2017). Assembly
of the Jacobian and residual, and the linear solve are parallelized using MPI which
allows Moltres to be run in massively parallel environments. Runs on the Blue Waters
supercomputer at Illinois have utilized up to 608 cores.
Moltres and MOOSE allow use of different basis functions for different system variables.
Because of the purely diffusive nature of the neutron diffusion equations, neutron fluxes are
typically discretized using continuous first-degree Lagrange polynomials and the degrees of
freedom are associated with mesh nodes. The temperature variable may also be discretized
with a continuous Lagrange basis, or a discontinuous basis of arbitrary degree monomials
may be employed depending on the relative balance of heat convection to conduction. The
purely hyperbolic precursor transport is currently discretized using constant monomials,
which is equivalent to a first-order finite volume discretization. Moltres supports both
segregated (through Picard iteration) and monolithic solutions of the equation system.
However, due to the feedback between the power spectrum and temperature dependence
of macroscopic cross-sections, monolithic solves have demonstrated superior robustness
with segregated techniques often unable to converge to a solution. This result emphasizes
the importance of a fully coupled multi-physics framework like the one that Moltres and
MOOSE provide and suggests that iteratively coupling codes devoted to single physics
(Kópházi, Lathouwers, and Kloosterman 2009) may result in limited flexibility.},
	number = {21},
	urldate = {2018-01-08},
	journal = {The Journal of Open Source Software},
	author = {Lindsay, Alexander and Huff, Kathryn},
	month = jan,
	year = {2018},
	pages = {1--2},
	file = {Full Text PDF:C\:\\Users\\Sun Myung\\Zotero\\storage\\MJIZZW4P\\Lindsay and Huff - 2018 - Moltres finite element based simulation of molten.pdf:application/pdf;Snapshot:C\:\\Users\\Sun Myung\\Zotero\\storage\\E3ARQ46H\\joss.html:text/html},
}

@article{lindsay_introduction_2018,
	title = {Introduction to {Moltres}: {An} application for simulation of {Molten} {Salt} {Reactors}},
	volume = {114},
	issn = {0306-4549},
	shorttitle = {Introduction to {Moltres}},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0306454917304760},
	doi = {10.1016/j.anucene.2017.12.025},
	abstract = {Moltres is a new physics application for modeling coupled physics in fluid-fuelled, molten salt reactors. This paper describes its neutronics model, thermal hydraulics model, and their coupling in the MOOSE framework. Neutron and precursor equations are implemented using an action system that allows use of an arbitrary number of groups with no change in the input card. Results for many-channel configurations in 2D-axisymmetric and 3D coordinates are presented and compared against other coupled models as well as the Molten Salt Reactor Experiment.},
	language = {en},
	urldate = {2018-01-08},
	journal = {Annals of Nuclear Energy},
	author = {Lindsay, Alexander and Ridley, Gavin and Rykhlevskii, Andrei and Huff, Kathryn},
	month = apr,
	year = {2018},
	keywords = {Reactor physics, Parallel computing, agent based modeling, Finite elements, Hydrologic contaminant transport, MOOSE, Multiphysics, nuclear engineering, Nuclear fuel cycle, Object orientation, repository, Simulation, Systems analysis},
	pages = {530--540},
	file = {Lindsay et al. - 2018 - Introduction to Moltres An application for simula.pdf:C\:\\Users\\Sun Myung\\Zotero\\storage\\RCWUNGTP\\Lindsay et al. - 2018 - Introduction to Moltres An application for simula.pdf:application/pdf;Lindsay et al. - 2018 - Introduction to Moltres An application for simula.pdf:C\:\\Users\\Sun Myung\\Zotero\\storage\\3GEC6NQ9\\Lindsay et al. - 2018 - Introduction to Moltres An application for simula.pdf:application/pdf;Moltres.pdf:C\:\\Users\\Sun Myung\\Zotero\\storage\\4XDXRICB\\Moltres.pdf:application/pdf;ScienceDirect Full Text PDF:C\:\\Users\\Sun Myung\\Zotero\\storage\\E2T9U5IX\\Lindsay et al. - 2018 - Introduction to Moltres An application for simula.pdf:application/pdf;ScienceDirect Snapshot:C\:\\Users\\Sun Myung\\Zotero\\storage\\3DT9TEY3\\S0306454917304760.html:text/html},
}

@article{park_verification_2022,
	title = {Verification of moltres for multiphysics simulations of fast-spectrum molten salt reactors},
	volume = {173},
	issn = {03064549},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0306454922001463},
	doi = {10.1016/j.anucene.2022.109111},
	abstract = {Modeling strongly coupled neutronics and thermal–hydraulics in liquid-fueled MSRs requires robust and ﬂexible multiphysics software for accurate simulations at reasonable computational costs. In this paper, we present Moltres and its neutronics and thermal–hydraulics modeling capabilities relevant to multiphysics reactor analysis. As a MOOSE-based application, Moltres provides various multiphysics coupling schemes and time-stepping methods, including fully coupled solves with implicit time-stepping. We veriﬁed Moltres’ MSR modeling capabilities against a multiphysics numerical benchmark developed for software dedicated to modeling fast-spectrum MSRs. The results show that Moltres performed comparably to participating software packages in the benchmark; the majority of the relevant quantities fell within one standard deviation of the benchmark average. Among the participating multiphysics tools in the benchmark, Moltres agrees closest to the multiphysics tool from the Delft University of Technology due to similarities in the numerical solution techniques and meshing schemes.},
	language = {en},
	urldate = {2022-04-26},
	journal = {Annals of Nuclear Energy},
	author = {Park, Sun Myung and Munk, Madicken},
	month = aug,
	year = {2022},
	pages = {109111},
	file = {Park and Munk - 2022 - Verification of moltres for multiphysics simulatio.pdf:C\:\\Users\\Sun Myung\\Zotero\\storage\\PHNTVU4R\\Park and Munk - 2022 - Verification of moltres for multiphysics simulatio.pdf:application/pdf},
}
